Involvement of proliferating cell nuclear antigen (cyclin) in DNA replication in living cells

Corneal Epithelial Deficiency Induced by the Use of β-Blocker Eye Drops

Two studies were conducted to check the effects of β-blocker eye drops, 2% carteolol (Mikelan®) and 0.5% timolol (Timoptol®), on regeneration of corneal epithelium in rabbit eyes. For the short-term study, epithelial deficiency was artificially induced in the cornea of albino rabbits. One of the β-blocker eye drops or 0.005% benzalkonium chloride was applied in the right eye and physiological saline solution was applied to the left eye four times a day, and wound healing rate was calculated. Two weeks later, images of the surface epithelium were analyzed by scanning electron microscopy and proliferative capacity was studied, using proliferating cell nuclear antigen as a marker. The long-term study was conducted similarly except that the eye drops were applied twice a day and epithelial deficiency was re-induced every two weeks.

In the short-term study, epithelial wound healing rate was slowed in β-blocker groups. Significant differences were detected between the Mikelan® and Timoptol® groups, and the benzalkonium and physiological saline groups. The β-blocker groups had severe epithelial cell desquamation, as well as detachment. In the long-term study, the Mikelan® group had significantly delayed wound healing at first induction, the benzalkonium group showed delay up to the third induction and the Timoptol® group up to the fifth induction. These studies indicate that β-blocker eye drops delay corneal epithelial wound healing and supported the concept that corneal epithelial deficiency occurs clinically after the long-term administration of β-blocker eye drops.

Dr Eng M. Tan: a tribute to an enduring legacy in autoimmunity

At the age of ninety years, Dr Eng Meng Tan has had a remarkable impact on the accumulated knowledge of autoimmune diseases, including seminal findings in systemic lupus erythematosus (SLE) and a wide range of other autoimmune diseases. Dating to the first description of the Sm (Smith) autoantibody in SLE, his focus has been the use of autoantibodies as probes to identify and elucidate novel cellular molecules and then translating these discoveries into biomarkers and immunoassays for a wide range of these diseases and, later, cancer. He led efforts to standardize autoantibody nomenclature and testing protocols. Through his mentorship a great number of trainees and collaborators have had remarkably successful careers, and by that virtue he has garnered a remarkable continuing legacy.

CAPER, a novel regulator of human breast cancer progression

CAPER is an estrogen receptor (ER) co-activator that was recently shown to be involved in human breast cancer pathogenesis. Indeed, we reported increased expression of CAPER in human breast cancer specimens. We demonstrated that CAPER was undetectable or expressed at relatively low levels in normal breast tissue and assumed a cytoplasmic distribution. In contrast, CAPER was expressed at higher levels in ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) specimens, where it assumed a predominantly nuclear distribution. However, the functional role of CAPER in human breast cancer initiation and progression remained unknown. Here, we used a lentiviral-mediated gene silencing approach to reduce the expression of CAPER in the ER-positive human breast cancer cell line MCF-7. The proliferation and tumorigenicity of MCF-7 cells stably expressing control or human CAPER shRNAs was then determined via both in vitro and in vivo experiments. Knockdown of CAPER expression significantly reduced the proliferation of MCF-7 cells in vitro. Importantly, nude mice injected with MCF-7 cells harboring CAPER shRNAs developed smaller tumors than mice injected with MCF-7 cells harboring control shRNAs. Mechanistically, tumors derived from mice injected with MCF-7 cells harboring CAPER shRNAs displayed reduced expression of the cell cycle regulators PCNA, MCM7, and cyclin D1, and the protein synthesis marker 4EBP1. In conclusion, knockdown of CAPER expression markedly reduced human breast cancer cell proliferation in both in vitro and in vivo settings. Mechanistically, knockdown of CAPER abrogated the activity of proliferative and protein synthesis pathways.

Humoral autoimmune response to IGF2 mRNA-binding protein (IMP2/p62) and its tissue-specific expression in colon cancer

To understand the autoimmune response and immunogenicity of a tumour-associated antigen (TAA) and IGF2 mRNA-binding protein (IMP2/62) in colon cancer, autoantibody to this TAA was evaluated by enzyme-linked immunosorbent assay (ELISA), Western blotting and indirect immunofluorescence assay in sera from patients with colon cancer. Immunohistochemistry (IHC) study with colon cancer tissues was also performed to analyse protein expression of IMP2/p62. The result has showed that there has a relatively higher frequency of autoantibody response to IMP2/p62 in colon cancer (23.4%, 15/64) compared to patients with colonic adenomas (4.8%, 2/42) and normal individuals (2.9%, 1/34). Of 64 colon cancer tissue specimens examined, 48 tissues (75.0%, 48/64) expressed p62, while normal colon tissues did not show any expression of p62 (0/34). The positive rate of antinuclear antibody (ANA) in colon cancer was 82.8% (53/64), which is significantly higher than that in patients with colonic adenomas (21.4%, 9/42) and normal individuals (17.6%, 6/34). The data suggest that the combinational detection of anti-p62 autoantibody and ANA is of significance in diagnosing colon cancer and monitoring the prognosis of the disease.

The HIV protease inhibitor lopinavir/ritonavir (Kaletra) alters the growth, differentiation and proliferation of primary gingival epithelium

OBJECTIVE

This study was designed to evaluate the effects of the HIV protease inhibitor lopinavir/ritonavir on gingival epithelium growth, integrity and differentiation.

METHODS

Organotypic (raft) cultures of gingival keratinocytes were established and treated with a range of lopinavir/ritonavir concentrations. To examine the effect of lopinavir/ritonavir on gingival epithelium growth and stratification, haematoxylin and eosin staining was performed. To investigate the effect of this drug on tissue integrity, transmission electron microscopy (TEM) was performed on untreated and drug-treated tissues. Further, immunohistochemical analysis of raft cultures was performed to assess the effect of lopinavir/ritonavir on the expression of key differentiation and proliferation markers including cytokeratins, proliferating cell nuclear antigen (PCNA) and cyclin A.

RESULTS

Lopinavir/ritonavir treatments drastically inhibited the growth of gingival epithelium when the drug was present throughout the growth period of the tissue. When the drug was added on day 8 of tissue growth, lopinavir/ritonavir treatments compromised tissue integrity over time and altered the proliferation and differentiation of gingival keratinocytes. Expression of cytokeratins 5, 14, 10 and 6, PCNA and cyclin A was induced, and their expression patterns were also altered over time in treated rafts.

CONCLUSIONS

The findings of our studies suggest that lopinavir/ritonavir treatments compromised tissue integrity over time and deregulated the cell cycle/proliferation and differentiation pathways, resulting in abnormal epithelial repair and proliferation. Our study provides a model of potential utility in studying the effects of antiretroviral drugs in vitro.

Effect of the HIV protease inhibitor amprenavir on the growth and differentiation of primary gingival epithelium

BACKGROUND

HIV-positive patients taking antiretroviral drugs, including protease inhibitors, have shown a significant increase in the development of oral complications; these complications are a major health issue for affected patients. The effect of these drugs on oral epithelium growth and differentiation is presently unknown. In this study, we explore for the first time the effect of the HIV protease inhibitor amprenavir on gingival epithelium growth and differentiation.

METHODS

Organotypic (raft) cultures of gingival keratinocytes were established and the raft cultures treated with a range of amprenavir concentrations. Haematoxylin and eosin staining was performed to examine the effect of amprenavir on gingival epithelium growth and stratification. The raft cultures were also immunohistochemically analysed to determine the effect of amprenavir on the expression of key differentiation and proliferation markers, including cytokeratins, proliferating cell nuclear antigen (PCNA) and cyclin A.

RESULTS

Amprenavir severely inhibited the growth of gingival epithelium when the drug was present throughout the growth period of the tissue. When the drug was added at day 8, amprenavir treatment altered the proliferation and differentiation of gingival keratinocytes. Expression of the cytokeratins 5, 14, 6 and 10, PCNA and cyclin A was increased; their expression pattern was also altered over time in treated rafts. Biochemically, the tissue exhibited characteristics of increased proliferation in the suprabasal layers of amprenavir-treated tissue.

CONCLUSIONS

Our results suggest that amprenavir treatment deregulates the cell cycle/proliferation and differentiation pathways, resulting in abnormal epithelial repair and proliferation. Our system could be developed as a potential model for studying the effects of highly active antiretroviral therapy in vitro.

Long-term effect of Spirulina platensis extract on DMBA-induced hamster buccal pouch carcinogenesis (immunohistochemical study)

In cancer research, the use of complementary and alternative medicine has increased over the past decade. In this study, 80 male golden Syrian hamsters were divided into four equal groups; the right buccal pouches of the hamster rats in group 1 were painted with 0.5% solution of 7, 12-dimethylbenz[a]anthracene (DMBA), three times a week for 32 weeks. The same pouches of group 2 were subjected to the same DMBA painting; but at the same time, the animals received 10 mg/daily Spirulina platensis extract for the same period. In group 3, the same regimen of DMBA painting was done but for 24 weeks only and the daily systemically S. platensis was received for the 32 weeks. In group 4, neither DMBA painting nor S. platensis administration was done but pouches were painted with saline and served as a control one. Five rats from each group were sacrificed at 12, 24, 28, and 32 weeks, respectively. The required pouches were excised, fixed, and embedded in paraffin to be immunostained with proliferating cell nuclear antigen (PCNA). The results showed that increased PCNA expression was directly related to the severity of pathological alterations from normal epithelium to dysplasia and from dysplasia to squamous cell carcinoma (SCC) in the study groups at the different extended periods of DMBA application and S. platensis extract administration. Analysis of variance and Duncan's multiple-range test for PCNA labeling index were proved a high significant difference (P < 0.01) between the different groups. From the previous results, it can be concluded that S. platensis extract has a beneficial role in regression of cancer progression.

Analysis of apoptosis and cell proliferation after high intensity-focused ultrasound ablation combined with microbubbles in rabbit livers

OBJECTIVE

To analyze apoptosis and expression of proliferating cell nuclear antigen (PCNA) sequentially in the rabbit liver tissue after high-intensity focused ultrasound (HIFU) ablation combined with microbubbles.

METHODS

Fifty rabbits were divided into two groups randomly. Rabbits in group I received injections with ultrasound contrast agent Sonovue, before HIFU ablation, on their livers and those in group II were ablated by a single HIFU exposure without microbubbles. Rabbits were killed on days 0, 1, 3, 7 and 14 after HIFU ablation. The livers were excised for light microscopic examination with hematoxylin and eosin staining, immunohistochemical staining for PCNA expression and terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick end labeling (TUNEL) staining for apoptosis.

RESULTS

A fibra tissue band composed of fibrocytes and capillary vessels, which was detected by light microscope in the rim of the targeted area after 3 days in group I, was wider than that in group II. The apoptosis index (the number of apoptotic events divided by the total cell number in the same field) and PCNA-positive index (the number of PCNA-positive cells divided by the total cell number in the same field) in group I on days 0, 1, 3, 7 and14 after HIFU ablation were higher than those in group II.

CONCLUSION

Microbubbles can improve the apoptosis and cell proliferation in zones surrounding coagulated necrosis areas after HIFU ablation, which may be explored to benefit enhanced HIFU treatment.

The effect of mandibular distraction osteogenesis on the histology and immunohistology of keratinized gingiva

OBJECTIVES

We investigated distracted keratinized epithelium to elucidate any proliferative and degenerated changes and to estimate the stability of the gingival tissues in mandibular distraction osteogenesis in a rabbit model.

STUDY DESIGN

Twenty-two rabbits were subjected to unilateral vertical osteotomy. After a latency period of 4 days, devices were activated 3, 6, and 10 days at a rate of 1 mm/day. We additionally investigated the recovery of the distracted gingiva in consolidation periods for 3 weeks. The animals were examined by histologic and immunohistologic methods using proliferating cell nuclear antigen (PCNA), single-stranded DNA (ssDNA), and keratin.

RESULTS

Atrophy of distracted gingiva was observed characterized by loss of rete ridges, acanthosis, vacuolation in the prickle cell layer, and cleavage of the keratin layer. Proliferating cell nuclear antigen-positive cells and ssDNA-positive cells were observed in the basal and prickle layers, respectively. During consolidation periods, slight recovery of rete ridges, thinning of the keratin layer, and immature epithelial layer was observed.

CONCLUSIONS

Proliferative and degenerated changes occurred to compensate for cell death and distracted space. Thickness of gingival tissues was maintained by high mitotic activity and delay in the rate of cell maturation. Immature epithelial layer was related to sensitive and weak resistance against various stimulating factors, such as cleavage of the keratin layer among distracted gingival tissues.

Study of sequential histopathologic changes, apoptosis, and cell proliferation in rabbit livers after high-intensity focused ultrasound ablation

OBJECTIVE

The purpose of this study was to investigate the sequential changes of rabbit liver tissue after high-intensity focused ultrasound (HIFU) ablation in histopathologic characteristics, apoptosis, and expression of proliferating cell nuclear antigen (PCNA).

METHODS

Thirty-five rabbits were anesthetized and received HIFU ablation on livers after laparotomy. Rabbits were killed at 0, 1, 24, 72, 144, 216, and 336 hours after HIFU ablation. The livers were cut off and examined under a light microscope with hematoxylin-eosin staining and under a transmission electron microscope. Proliferating cell nuclear antigen expression was detected by immunohistochemical staining, and apoptosis was observed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL).

RESULTS

After HIFU ablation, fibra bands were detected under the light microscope in the rim of targeted areas after 72 hours, and the band became wide sequentially. Cells labeled by TUNEL and PCNA-positive cells were detected to different extents in surrounding tissues but not in targeted areas at 0, 1, 24, 72, 144, 216, and 336 hours after HIFU ablation. The apoptosis index detected by TUNEL reached a peak value at 72 hours after ablation, and the highest PCNA-positive index was found at 144 hours after ablation. Apoptotic bodies and oncotic mitochondria in surrounding areas were observed under the electron microscope.

CONCLUSIONS

After HIFU ablation, coagulated necrotic tissues became organized and fibra encapsuled gradually. Apoptosis and cell proliferation were detected in surrounding areas, which provided some implications for controlling HIFU treatment, although thermometry was not done to correlate the HIFU region with the cellular damage region, limiting correlation of the results.

Pathobiology of Pituitary Adenomas and Carcinomas

OBJECTIVE

To examine relationships between pituitary tumors and lesion size, invasiveness, resectability, deoxyribonucleic acid ploidy, cell cycle profile, mitotic activity, and immunoreactivity for MIB-1, proliferating cell nuclear antigen (PCNA), p27Kip1, and p53.

PATIENTS AND METHODS

One hundred fifty-three adenomas of most pathological subtypes, including 20 medically treated and prolactin and growth hormone-containing tumors, as well as 10 premetastatic tumors and 13 pituitary carcinomas, were studied.

RESULTS

Significant (P < 0.05) differences were noted between functional versus nonfunctional adenomas (percent aneuploidy, percent S phase, p27Kip1 labeling indices [LI], male sex, tumor size, and frequency of visual disturbance); Cushing's versus silent adrenocorticotropin adenomas (percent hypertetraploidy, p53 LI, tumor size, visual disturbance, and resectability); untreated versus medically treated prolactin cell adenomas (MIB-1 LI, p53 LI, and resectability); untreated versus medically treated growth hormone-containing adenomas (percent diploidy, percent S phase, MIB-1 LI, p53 LI, and p27 LI); untreated prolactin cell adenomas versus premetastatic tumors (percent hypertetraploidy, PCNA LI, p53 LI, invasiveness, and resectability); untreated growth hormone-containing adenomas versus premetastatic tumors (percent diploidy, percent S phase, PCNA LI, p53 LI, invasiveness, and resectability); Cushing's adenomas versus premetastatic tumors (percent diploidy, percent hypertetraploidy, percent S phase, MIB-1 LI, p53 LI, tumor size, invasiveness, visual disturbance, and resectability); Nelson's adenomas versus premetastatic tumors (p53 LI, tumor size, invasiveness, and resectability); silent adenomas as a whole versus nonfunctional adenomas (percent nondiploid, percent S phase, invasiveness, and respectability); silent adrenocorticotropin adenomas I and II versus silent adenoma Subtype III (invasiveness); silent adrenocorticotropin adenoma Subtypes I and II versus premetastatic tumors (MIB-1 LI and invasiveness); silent adenoma Subtype III versus premetastatic tumors (PCNA and p53 LI); and premetastatic tumors versus metastatic pituitary carcinomas (MIB-1 LI).

CONCLUSION

Only trends toward differences were noted between Cushing's versus Nelson's adenomas and between prolactinomas of reproductive female patients versus those of menopausal female patients and male patients. Too few "atypical adenomas" were encountered to permit their comparison with premetastatic tumors, but our results suggest that most pituitary carcinomas arise by malignant transformation from adenomas.

Higher expressions of p53 and proliferating cell nuclear antigen (PCNA) in atrophic oral lichen planus and patients with areca quid chewing

OBJECTIVE

The aim of the study was to examine the expressions of p53 and proliferating cell nuclear antigen (PCNA) in oral lichen planus (OLP) in relation to its clinical behavior and the patients' oral habits.

STUDY DESIGN

Immunohistochemical study was carried out to investigate the expressions of p53 and PCNA in 56 OLP specimens. The results were correlated with the clinical behavior of the disease and the patients' oral habits. The expression rates were further compared with those of normal oral mucosa (NOM), epithelial hyperkeratosis (EH), epithelial dysplasia (ED), and squamous cell carcinoma (SCC).

RESULTS

The staining rate of p53 (28.6%) and PCNA labeling index (LI) (27.6 +/- 8.8%) in OLP were similar to those in EH ( P = .868, .074, respectively), but higher than those of NOM and lower than those of ED and SCC (all P < .05). In OLP, no significant correlations were found between p53 or PCNA expression and the patients' age, gender, lesion duration, location, size, number of site, presence of pain, presence of local irritant, and the habits of alcohol drinking and cigarette smoking (all P > .05). In addition, the mean PCNA LI of p53+ cases was close to that of p53- cases (P = .38). However, the staining rate of p53 in OLP was higher in areca quid (AQ) chewers compared to abstainers (P = .001), and the mean PCNA LI in atrophic cases was higher than that in hypertrophic cases (P = .029). Interestingly, the staining rate of p53 and mean PCNA LI were significantly increased in AQ chewers with atrophic OLP (100%, 36.7% +/- 9.0%, respectively), which were similar to those in ED and SCC (all P > .05).

CONCLUSIONS

Although this study could not confirm the precancerous nature of OLP by the relatively low p53 and PCNA expression, the results do suggest that atrophic form OLP and patients with AQ chewing habit may have a higher disease activity in view of higher expression rates of p53 and PCNA in the lesions.

Dominant-negative cAMP-responsive element-binding protein inhibits proliferating cell nuclear antigen and DNA repair, leading to increased cellular radiosensitivity

Selective inhibition of the epidermal growth factor receptor or mitogen-activated protein kinase (MAPK) results in radiosensitization of cancer cells. One potential mechanism involves cAMP-responsive element-binding protein, which is activated by radiation via the epidermal growth factor receptor/MAPK pathway and which regulates synthesis of proliferating cell nuclear antigen (PCNA), a protein involved in repair of ionizing radiation-induced DNA damage. To test for a role of CREB in cellular radiosensitivity, CHO cells were transfected with plasmids expressing dominant-negative CREB mutants (CR133 or KCREB), and various end-points were measured 48 h later. Basal levels of PCNA-CAT reporter construct activity were reduced by 60 and 40% following expression of CR133 and KCREB, respectively; similar decreases were observed in PCNA protein levels. Pulsed-field gel electrophoresis measurements showed that CR133 inhibited the repair of radiation-induced DNA double-strand breaks, and this effect was reversed by over-expression of PCNA; dominant-negative CREB also significantly inhibited split-dose recovery. Clonogenic assays were used to determine surviving fraction; the dose enhancement ratios for dominant-negative CREB-expressing cells compared with control (vector alone) were 1.5 and 1.3 for CR133 and KCREB, respectively. Importantly, co-transfection of mutant CREB and a construct constitutively expressing PCNA protein restored radiosensitivity of CHO cells back to wild-type levels. Moreover, cells expressing either CREB mutant showed no significant cell cycle redistribution. These data demonstrate that genetic disruption of CREB results in radiosensitization, and that this effect can be explained by a mechanism involving decreased PCNA expression and inhibition of DNA repair.

Autoimmune responses to proliferating cell nuclear antigen multiprotein complexes involved in cell proliferation are strongly associated with their structure and biologic function in patients with systemic lupus erythematosus

OBJECTIVE

To analyze the reaction of lupus sera with proliferating cell nuclear antigen (PCNA) multiprotein complexes (PCNA complexes), which are part of the protein machinery involved in cell proliferation.

METHODS

PCNA complexes were purified from rabbit thymus extract by affinity chromatography using anti-PCNA monoclonal antibodies (TOB7, TO17, and TO30); monomeric and trimeric PCNA forms (AK-PCNA) were purified using anti-PCNA serum AK. The reactions to these antigens of 10 anti-PCNA-positive and 40 anti-PCNA-negative sera selected from 560 lupus patients were tested by immunoblotting, immunoprecipitation, and enzyme-linked immunosorbent assays (ELISAs).

RESULTS

With one exception (serum OK), anti-PCNA-positive sera reacted exclusively with only the 34-kd polypeptide. In contrast, 14 of 40 anti-PCNA-negative sera reacted with multiple proteins within PCNA complexes. Most anti-PCNA-positive sera probably recognize as epitopes the binding sites for other proteins on PCNA, which are likely hidden when PCNA is complexed with other proteins. As a consequence, only serum OK reacted with the PCNA complex in a series of ELISAs. Using AK-PCNA as a competitive inhibitor, it was determined that serum OK reacts with both the 58-kd polypeptide and the 34-kd PCNA within complexes. Together with the results of a longitudinal analysis, these results suggest that the immune system of patient OK likely recognized the complexed PCNA protein, after which the autoimmune response spread to other elements of the complexes.

CONCLUSION

Intermolecular-intrastructural help, leading to the spread of autoimmune response from PCNA to other proteins associated with its biologic function, plays a crucial role in the induction of the autoimmune response seen in lupus patients.

Rainbow trout primary epidermal cell proliferation as an indicator of aquatic toxicity: an in vitro/in vivo exposure comparison

Little or no work has been carried out on primary cell cultures in terms of cellular proliferation and toxicity studies. Cell proliferation represents one of the most relevant cellular functions. Anti-PCNA antibodies have aroused considerable interest recently as potential immunocytochemical markers of proliferation for use in toxicity studies. In this study, PCNA methodology, which was developed primarily for mammalian tissues, was adapted to rainbow trout (Oncorhynchus mykiss (R.)) primary cultured epidermal cells exposed in vivo i.e. whole animal exposures and in vitro for the study of the ecotoxicological potential of the aromatic amine, 2,4-dichloroaniline (2,4-DCA), a member of a little studied and widespread class of aquatic pollutants. There are many approaches to assess the proliferative activity of cells. Immunocytochemical methods offer a high sensitivity and specificity. The immunohistochemical avidin-biotin complex (ABC) method was used for the detection and quantification of PCNA, one of the best-known endogenous proliferation markers, applying the mammalian monoclonal antibody PC-10 to formalin-fixed primary cultures of rainbow trout skin. Here we describe our experience with the immunocytochemical detection and quantification of this proliferation marker. Results indicate that the antibody cross reacts with the corresponding rainbow trout epitope and that the alterations in PCNA labelling in the in vivo and in vitro exposed cultures followed similar patterns. This paper presents data on the validation of rainbow trout primary epidermal culture as an in vitro ecotoxicity model with epidermal proliferation as an endpoint. It can be concluded that cellular proliferation could be used as an indicator of the aquatic toxicity potential of xenobiotics. Correlations between cellular proliferation responses in primary cultures derived from in vivo exposed rainbow trout and primary cultures exposed in vitro were assessed. A dose-response was evidenced in both approaches, however the in vivo exposures appeared to be approximately two orders of magnitude more sensitive than the in vitro exposures. Responses in vitro occurred between 200 and 1000 micro M while in vivo responses were between 2 and 10 micro M. The good qualitative correspondence between the in vitro and in vivo results indicates that studies using trout epidermal cells allow the identification of xenobiotic effects in fish skin. However, further work is required before quantitative predictions i.e. effective concentrations in vivo, can be made from in vitro studies. This study suggests that the in vitro exposed rainbow trout primary cultured cell model with proliferation as an endpoint can be used as an alternative testing procedure to the whole animal assay.

Human proteomic databases: a powerful resource for functional genomics in health and disease

Decoding of the genome information in terms of regulation and function will be the next great challenge in the life sciences in this millennium and indeed, today we are experiencing a rapid explosion of technology for the high throughput expression analysis of genes and their products (functional genomics). In particular, the field of proteomics is booming as proteins are often the functional molecules and represent important targets for the pharmaceutical industry. The proteomic technology is complex, and comprises a plethora of state-of-the-art techniques to resolve, identify and detect their interacting partners, as well as to store and communicate protein information in comprehensive two-dimensional polyacrylamide gel electrophoresis (2D PAGE) databases. Besides annotating the genome, these databases will offer a global approach to the study of gene expression both in health and disease. Here, we review the current status of human 2D PAGE databases that we are systematically constructing for the study of bladder cancer and skin ageing.

Targeting of PCNA to sites of DNA replication in the mammalian cell nucleus

We have examined the targeting of proliferating cell nuclear antigen (PCNA), an integral component of the mammalian replicative enzyme DNA polymerase delta, with sites of DNA replication by using confocal microscopy and computer image analysis. Labeling (5 min pulse) of DNA replication sites in normal human diploid fibroblast cells (NHF1) with BrdU was followed by immunostaining with PCNA antibodies. A striking degree of colocalization was seen between PCNA and the characteristic patterns of DNA replication sites of early, middle and late S-phase (Nakayasu and Berezney [1989] J. Cell. Biol. 108:1-11). These observations were confirmed by quantitative computer image analysis which revealed that approximately 90% of the PCNA-stained area overlapped with DNA replication sites in early S-phase. Pulse-chase experiments, involving in vivo labeling for replication followed by PCNA staining at later time points, suggested that PCNA disassembles from previously replicated sites and targets to newly active sites of DNA replication. To further study this phenomenon in living cells, stable GFP-PCNA transfectants under the control of a tetracycline-inducible promoter were created in mouse 3T6 cells. Like the endogenous PCNA, GFP-PCNA targeted to sites of replication (approximately 80% colocalization) and demonstrated similar dynamic changes following pulse-chase experiments in fixed cells. Studies of living cells revealed progressive changes in the GFP-PCNA distribution that mimic the replication patterns observed in fixed cells. We conclude that GFP-PCNA targets to DNA replication sites in living cells and is an effective marker for tracking the spatio-temporal dynamics of DNA replication as cells transverse the S-phase.

Reactivity of anti-proliferating cell nuclear antigen (PCNA) murine monoclonal antibodies and human autoantibodies to the PCNA multiprotein complexes involved in cell proliferation

Proliferating cell nuclear Ag (PCNA) occurs as a component of multiprotein complexes during cell proliferation. We found the complexes to react with murine anti-PCNA mAbs, but not with anti-PCNA Abs in lupus sera. The complexes were purified from rabbit thymus extract by affinity chromatography using anti-PCNA mAbs (TOB7, TO17, and TO30) and analyzed by ELISA, immunoprecipitation, immunoblotting, and HPLC gel filtration. That PCNA was complexed with other proteins was demonstrated by its copurification with a group of proteins excluded by an HPLC G3000 SW column. Although immunoblot analysis showed the mAbs to react exclusively with the 34-kDa PCNA polypeptide, they nonetheless immunoprecipitated the same group of proteins, confirming the interaction of the isolated PCNA with other proteins. Anti-PCNA sera, including AK, which reacts with biologically functional sites on PCNA, did not react with complexed PCNA, but did react with it once it was dissociated from the complexes. PCNA complexes in turn reacted with murine anti-DNA mAbs, as well as with Abs against p21, replication protein A, DNA helicase II, cyclin-dependent kinases 4 and 5, and topoisomerase I. These findings suggest that the PCNA complexes purified using anti-PCNA mAbs comprise the "protein machinery" for DNA replication and cell cycle regulation. They also suggest that anti-PCNA mAbs are useful tools with which to characterize the protein-protein interactions within PCNA complexes, as well as the autoimmune responses to proteins interacting with PCNA, which may shed light on the mechanisms of autoantibody production in lupus patients.

Proliferating cell nuclear antigen and p53 protein expression in submucosal invasive colorectal carcinoma

In some cases of early colorectal carcinoma, radical surgical resection might be required because of vessel invasion, distant metastasis, or inadequate surgical margin. To characterize submucosal invasive colorectal carcinoma, we investigated expression of PCNA and p53 protein. Sixty-seven patients who underwent curative resection of submucosal invasive colorectal carcinoma participated in this study. The PCNA labeling index (PCNA-LI) is determined at the deepest lesion of carcinoma. The expression of PCNA and p53 protein were analyzed according to clinicopathological factors. 1) The PCNA-LI was correlated to histological grade, depth of invasion or vessel invasion in polypoid type. 2) The flat type had significantly higher PCNA-LI (65.1+/-8.2%) and p53 protein expression (69.6%) than the polypoid type. 3) The PCNA-LI was higher in cases with lymph node metastasis than in these without lymph node metastasis. 4) Overexpression of the p53 protein was detected in all cases with liver metastasis. Our results suggest that in order to determine the treatment for the patients with submucosal invasive colorectal carcinoma, the expression of PCNA and p53 protein may be a useful biologic marker.

Morphologic progression of polypoid colon cancer invading muscularis propria

To clarify the morphologic progression of polypoid growth in colon cancer invading the musculasris propria, we assessed the morphologic changes in 50 such cancers according to the size and shape of the polyp. The shape of the head of the polyp was defined at the widest slice as semicircular or ulcerated. As the cancer invaded the musculasris propria, the head of the polyp thickened and the structure of the head progressively collapsed, causing its shape to change from semicircular to ulcerated. The proliferating cell nuclear antigen percentage of cells with positively stained nuclei labeling index, determined at the deepest point of invasion, significantly correlated with the morphologic progression of the polyp from semicircular to ulcerated (63.2 +/- 6.7% and 74.9 +/- 7.2%, respectively; P < 0.05). These results indicate that the proliferating cell nuclear antigen labeling index may be a useful marker for the morphologic progression of invasive colonic polyps.

Immunohistochemical analysis of apoptosis-related proteins in human embryonic and fetal pancreatic tissues

BACKGROUND

The growth of both cancer cells and fetal tissue is rapid; however, cancer cells de-differentiate and proliferate in a disorderly manner, whereas fetal tissues differentiate and proliferate in an orderly manner. Thus, there may be both common and different factors that are involved in the process of the uncontrolled cell growth of pancreatic cancers and the development of the fetal pancreas. The common part of the mechanisms should be in the regulation of the cell cycle, resulting in rapid proliferation via such mechanisms as growth stimulation and avoidance of apoptosis. Therefore, in the current study we investigated the expression of apoptosis-related proteins in fetal pancreatic tissues.

METHODS

Sixteen human embryonic and fetal pancreatic tissues obtained between 6 and 32 wk of gestation were used. We immunohistochemically examined the protein expression of Bcl-2, Bcl-XL, Mcl-1, and Bax. Further, the expression of insulin, glucagon, and proliferting cell nuclear antigen (PCNA), and TdT-mediated dUTP-biotin nick-end labeling (TUNEL) staining were examined.

RESULTS

In embryonic and fetal pancreatic tissues, Bcl-2 was not detected in any type of pancreatic cell (acinar, ductal, or islet). Bcl-XL was expressed in all types of pancreatic cells throughout the gestation. Mcl-1 was expressed in all types of pancreatic components, and strongly expressed in the margin of the islets. Bax, a pro-apoptotic protein, was expressed in all components. PCNA was strongly expressed in the embryonic and fetal pancreas, especially in early stages of gestation; however, TUNEL staining was negative in all samples. At least one antiapoptotic protein was expressed in all types of pancreatic cells.

CONCLUSION

The results of the current study indicate that active proliferation and avoidance of apoptosis take place in embryonic and fetal pancreatic tissues, which may be controlled by particular combinations of apoptosis-related proteins. Among these proteins, Bcl-XL and Mcl-1 may play an important role in the proliferation and differentiation of the embryonic and fetal pancreas.

Prognostic significance of cyclin D1 protein levels in early-stage larynx cancer treated with primary radiation

Recent laboratory experiments have demonstrated that cyclin D1 levels (cycD1) can influence radiosensitivity. The purpose of the current study is to evaluate the prognostic significance of cycD1 for local recurrence in early-stage larynx cancer treated with primary radiation therapy. The study was conducted using a matched case-control design in 60 early-stage (T1-T2/N0) larynx cancer patients. All patients had squamous cell carcinoma of the larynx and were treated with primary radiation to a total median dose of 66 Gy in daily fractions of 2 Gy, without surgery or chemotherapy. Thirty patients who suffered a local relapse in the larynx after treatment served as the index case population. These 30 cases were matched by age, sex, site (glottic vs. supraglottic), radiation therapy technique/dose, and follow-up, to 30 control patients who did not experience a local relapse. Immunohistochemical staining from cycD1 was performed on the paraffin-embedded specimens. The pathologist, blinded to the clinical information, scored each of the specimens on a four-point intensity scale (0 = no stain, 1 = faint, 2 = moderate, 3 = strong) and percent distribution. Patients were considered to be positive for cyclin D1 if the staining was 2+ or greater with a percent distribution of at least 5%. By design of the study, the two groups were evenly balanced with respect to age, sex, stage, radiation dose, and follow-up. CycD1 levels correlated with proliferating cell nuclear antigen levels. Low levels of cycD1 significantly correlated with local relapse; 19/30 (63%) of the index cases stained negative, while only 10/30 (33%) of the control cases stained negative (P = 0.03). These data suggest that low levels of cycD1 correlate with relatively radioresistant early-stage larynx carcinoma. With larger more confirmatory clinical and laboratory data, this data may have significant clinical implications. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 22-28 (2000).

Morphologic progression of pedunculated submucosal invasive colon cancer

To clarify the morphologic progression of pedunculated submucosal invasive colon cancers, we assessed the morphologic changes in 50 such cancers according to the volume of cancer in the submucosal layer. The shape of the head of the polyp was defined at the widest slice as round, concave, or semicircular with a horizontal head (SHH). As the cancer invaded the submucosa, the peduncle of the submucosal invasive cancer thickened and the structure of the head progressively collapsed, causing its shape to change from round to concave to SHH. The proliferating cell nuclear antigen (PCNA) expression (labeling index, LI), determined at the deepest point of submucosal invasion, showed a significant correlation with the morphologic progression among round, concave, and SHH cancers as 36.4 +/- 12.1%, 42.3 +/- 11.8%, and 62.1 +/- 12.5%, respectively (P < 0.05). Results indicate that the PCNA-LI may be a useful marker for the morphologic progression of pedunculated submucosal invasive colon cancers.

Mapping of topoisomerase II alpha epitopes recognized by autoantibodies in idiopathic pulmonary fibrosis

Autoantibodies against DNA topoisomerase II alpha have been identified in the sera of patients with idiopathic pulmonary fibrosis (IPF). To map topoisomerase II autoepitopes, we tested by ELISA and immunoblotting the IPF anti-topoisomerase II-positive sera against a series of recombinant proteins which covered the full length of topoisomerase II alpha. Specific patterns of reactivity were observed, indicating the existence of multiple epitopes on topoisomerase II, either highly complex or conformational/discontiguous or conformational/contiguous ones. The latter resided in amino acid residues 854-1147 and 1370-1447. A detailed analysis of these regions was undertaken, but we were not able to pinpoint a sequential peptide-sized epitope, or any significant homology with foreign pathogens. Further, we observed a significant correlation between the progression from a contiguous to a quaternary/tertiary structure-dependent autoepitope and the disease duration but not with the disease severity. Therefore, this result supports the hypothesis that anti-topoisomerase II autoreactivity evolves following an antigen-driven process.

Multiple roles of the proliferating cell nuclear antigen: DNA replication, repair and cell cycle control

The proliferating cell nuclear antigen (PCNA), the auxiliary protein of DNA polymerase delta and epsilon, is involved in DNA replication and repair. This protein forms a homotrimeric structure which, encircling DNA, loads the polymerase on the DNA template. A role for PCNA in the cell cycle control is recognised on the basis of the interaction with cyclins, cyclin-dependent kinases (cdks) and the cdk-inhibitor p21 waf1/cip1/sdi1 protein. Association with the growth-arrest and DNA-damage inducible proteins gadd45 and MyD118, further demonstrates the role of PCNA as a component of the cell cycle control apparatus.

Proliferating cell nuclear antigen as a marker of cell kinetics in aberrant crypt foci, hyperplastic polyps, adenomas, and adenocarcinomas of the human colon

BACKGROUND

One of the first steps in multistage colonic carcinogenesis is increased cell proliferation and an upward shift of the proliferation zone of colonic crypts. In the present study, progression in cell kinetics was followed up at all sequential stages of colonic carcinogenesis, starting with aberrant crypt foci (ACF), the earliest putative preneoplastic lesions, hyperplastic and dysplastic polyps, and invasive carcinomas.

MATERIALS AND METHODS

Colonic tissue and tumor specimens were prospectively obtained from 65 patients treated at our hospital for adenocarcinoma or malignant polyps. For identification of ACFs, dissected mucosal strips obtained from patients with colorectal cancer were stained with 0.1% methylene blue and scanned under dissecting microscope. Paraffin-embedded ACFs and macroscopic lesions were serially sectioned, deparaffinized, and stained with a monoclonal antiproliferating cell nuclear antigen (PCNA) antibody. The PCNA-labelling index (PCNA-LI), expressed as a ratio of positively stained nuclei to total nuclei counted, was calculated separately for basal, middle, and upper colonic crypt compartments. A comparison of the PCNA-LI was made for each compartment in normal mucosa, and hyperplastic and dysplastic lesions.

RESULTS

A stepwise increase in the PCNA-LI was observed during neoplastic progression of colonic lesions. The two most important variables of increased cell proliferation, expressed as PCNA-LI per crypt compartment, were the presence of dysplasia and the size of dysplastic lesions.

CONCLUSIONS

In colorectal carcinogenesis, hyperproliferation with upward expansion of proliferative compartment is a characteristic feature at all stages of malignant progression.

Nocturnal urinary 6-sulfatoxymelatonin and proliferating cell nuclear antigen-immunopositive tumor cells show strong positive correlations in patients with gastrointestinal and lung cancer

The hormone melatonin plays a key role in coordinating neuroendocrine signals involved in the control of biological rhythms and also appears to be involved in the regulation of cellular proliferation. In this study on patients with gastrointestinal and lung cancer the nocturnal urinary excretion of 6-sulfatoxymelatonin (aMT6s) reflecting pineal melatonin production as well as immunohistochemically detectable proliferating cell nuclear antigen (PCNA) and melatonin were measured in corresponding tumor specimens (6 colorectal, 8 stomach, and 12 lung cancers). Strong positive correlations were detected between aMT6s and PCNA for the different types of tumors analysed (1 > or = Rs > or = 0.736, P < 0.01-0.0001). These findings provide support to the concept of an involvement of the pineal gland in malignancy and suggest that aMT6s-measurements may be considered as a non-invasive tool to estimate tumor cell proliferation. Negative correlations found between urinary aMT6s and melatonin in tumor cells (-0.735 > or = Rs > or = -0.928, P < 0.01-0.0025) could be interpreted as an effort of the pineal gland to secrete melatonin to compensate for the decrease in the number of melatonin-immunopositive cells within tumor tissue where it may possess important regulatory functions.

Expression of the POU transcription factor Brn-5 inhibits proliferation of NG108-15 cells

The POU domain transcription factors are a subgroup of homeodomain proteins that appears to control cellular phenotypes. The expression of the POU protein Brn-5 occurs selectively in postmitotic CNS neurons. Ectopic expression of Brn-5 in dividing NG108-15 cells reduces the level of RNA encoding the proliferating cell nuclear antigen (PCNA). This ectopic expression also inhibits DNA synthesis as measured by the incorporation of bromodeoxyuridine (BrdU). Thus, Brn-5 may inhibit the continued proliferation of these cells. A potential function of Brn-5 may be to suppress the action of proliferative signals in postmitotic neurons and thus prevents them from reentering the cell cycle.

High PCNA index in meningiomas resistant to radiation therapy

PURPOSE

Meningiomas are common intracranial tumors, often well controlled with surgical resection alone. While the efficacy of radiation therapy in improving local control and progression-free survival is well documented, prognostic data substantiate factors that are predictive of poor local control following definitive radiation therapy. PCNA is a DNA polymerase expressed at the highest levels in the S-phase, the most resistant portion of the cell cycle to ionizing radiation in vitro. We investigated the possible correlation between the levels of PCNA expression and the clinical outcome of patients treated with definitive radiation therapy.

METHODS AND MATERIALS

Archival tissue was collected from 33 cases of meningioma treated at our institution for definitive radiation therapy between 1970 and 1990. Age-matched normal meningeal tissue and asymptomatic meningiomas removed at autopsy served as tissue controls. A standard ABC immumoperoxidase technique employing antibodies to PCNA, PC-10 (Dako, California) was used to stain specimen slides for PCNA. PCNA index was defined as the number of positive nuclei per 10 high-power fields at 400x magnification. Two independent observers scored the slides without prior knowledge of the cases at hand.

RESULTS

Patients with high PCNA index were less likely to be controlled by therapeutic radiation (p < 0.001, Kaplan-Meier). All patients with a PCNA index greater that 25 failed radiation therapy. Using multivariate analyses, malignant (but not atypical), histology and PCNA index were significant predictors of progression following radiation therapy (p < 0.05, log rank).

CONCLUSION

PCNA index may be a useful adjunct to more standard histopathologic criteria in the determination of meningioma local control and progression-free survival following therapeutic irradiation. Data on a more expanded population evaluated on a prospective basis will be needed before such criteria are routinely employed in the clinical setting.

Effect of passage number on cellular response to DNA-damaging agents: cell survival and gene expression

The effect of different passage numbers on plating efficiency, doubling time, cell growth, and radiation sensitivity was assessed in Syrian hamster embryo (SHE) cells. Changes in gene expression after UV or gamma-ray irradiation at different passage numbers were also examined. The SHE cells were maintained in culture medium for up to 64 passages. Cells were exposed to 60Co gamma rays or 254-nm UV radiation. Differential display of cDNAs and Northern blots were used for the study of gene expression. With increasing passage number, SHE cells demonstrated decreased doubling time, increased plating efficiency, and a decreased yield in the number of cells per plate. Between passages 41 and 48 a 'crisis' period was evident during which time cell growth in high serum (20%) was no longer optimal, and serum concentrations were reduced (to 10%) to maintain cell growth. Sensitivity to ionizing radiation was no different between early- and intermediate-passage cells. However, after UV exposure at low passages (passage 3), confluent cells were more sensitive to the killing effects of UV than were log-phase cells. At intermediate passages (passages 43, 48), confluent cells were slightly more radioresistant than were log-phase cells. By passage 64, however, both confluent and log-phase cells showed similar patterns of UV sensitivity. Expression of gamma-actin, PCNA, and p53 transcripts did not change following UV exposure. p53 mRNA was induced following gamma-ray exposure of the intermediate (passage 45) epithelial cells. The observed differences in radiation sensitivity associated with increasing passage number may be influenced by radiation-induced gene expression. We are conducting experiments to identify these genes.

Proliferating cell nuclear antigen expression and its relationship to malignancy potential in invasive colorectal carcinomas

PURPOSE

Cellular proliferative activity is a useful indicator of biologic aggressiveness in colorectal carcinoma. Immunohistochemical analysis of proliferating cell nuclear antigen (PCNA) has important advantages of maintaining tissue architecture and technical simplicity. The aim of this study was to investigate the correlation between proliferative activity and malignancy potential in colorectal carcinomas to determine whether proliferative index of cancer cells has prognostic significance using immunohistochemical technique.

METHODS

Proliferation index at the invasive tumor margin of 86 paraffin sections of advanced colorectal carcinomas was assessed by immunohistochemical study using a mouse monoclonal antibody to PCNA (PC-10) and was compared with conventional clinicopathologic factors and other possible prognostic parameters, including p53 overexpression, tissue carcinoembryonic antigen immunoreactivity pattern, and flow cytometric DNA ploidy. In addition, recurrence and survival were analyzed in accordance with degree of PCNA expression.

RESULTS

PCNA labeling index (PCNA-LI) increased significantly as the Astler-Coller stage advanced (P = 0.0001). Strong correlations were observed between PCNA-LI and various pathologic parameters, including histologic differentiation (P = 0.0027), lymphatic invasion (P = 0.0001), vascular invasion (P = 0.0001), lymph node metastasis (P = 0.0001), and liver metastasis (P = 0.0036). Mean PCNA-LI was also significantly higher in tumors with DNA aneuploidy (P = 0.0006) and negative and cytoplasmic patterns of carcinoembryonic antigen immunoreactivity (P = 0.01). Linear relationships were demonstrated between PCNA-LI and clinical outcomes; recurrence rate was significantly greater in the group with higher than the mean PCNA-LI, who underwent curative resection (P < 0.01), and four-year survival rates for both overall and curative cases with higher than the mean PCNA-LI were significantly poorer than those with lower than mean PCNA-LI (P < 0.005 and P < 0.01, respectively).

CONCLUSION

Evaluation of PCNA-LI at the invasive tumor margin in colorectal carcinomas is suggested to be valuable in predicting those people with a higher potential for metastasis and recurrence after surgery; thus, the evaluation is helpful in planning reasonable adjuvant therapy, even in the earlier stages.

17beta-Estradiol metabolites affect some regulators of the MCF-7 cell cycle

The activity of p34(cdc2) plays a key role in the regulation of the eukaryotic cell cycle. Another cell cycle associated molecule is PCNA. We investigated the effects of 2-hydroxy-17beta-estradiol, a cell proliferator, and 2-methoxy-17beta-estradiol, a potent inhibitor of cell growth, on the levels and activity of p34(cdc2) and on the levels of PCNA, as well as on protein phosphorylation in MCF-7 cells. 2-Hydroxyestradiol increased p34(cdc2) activity at G1/S and elevated PCNA levels during S-phase. 2-Methoxyestradiol caused unscheduled activation of p34(cdc2) in S-phase and decreased levels of p34(cdc2) and PCNA during G2/M. We conclude that 2-hydroxy- and 2-methoxyestradiol have definite, though different regulatory functions during the cell cycle.

rTP: a candidate telomere protein that is associated with DNA replication

In this paper we describe the isolation and characterization of rTP, the replication Telomere Protein, formerly known as the telomere protein homolog. The rTP was initially identified because of its homology to the gene for the Oxytricha telomere-binding protein alpha-subunit. The protein encoded by the rTP gene has extensive amino acid sequence identity to the DNA-binding domain of the telomere-binding proteins from both Euplotes crassus and Oxytricha nova. We have now identified the protein encoded by the rTP gene and have shown that it differs from the telomere-binding protein in its abundance, solubility and intracellular location. To learn more about the function of rTP, we determined when during the Euplotes life cycle the gene is transcribed. The transcript was detectable only in nonstarved vegetative cells and during the final stages of macronuclear development. Since the peak transcript level coincided with the rounds of replication that take place toward the end of macronuclear development, it appeared that rTP might be involved in DNA replication. Immunolocalization experiments provided support for this hypothesis as antibodies to rTP specifically stain the replication bands. Replication bands are the sites of DNA replication in Euplotes macronuclei. Our results suggest that rTP may be a new telomere replication factor.

Regulation of the cell cycle following DNA damage in normal and Ataxia telangiectasia cells

A proportion of the population is exposed to acute doses of ionizing radiation through medical treatment or occupational accidents, with little knowledge of the immediate effects. At the cellular level, ionizing radiation leads to the activation of a genetic program which enables the cell to increase its chances of survival and to minimize detrimental manifestations of radiation damage. Cytotoxic stress due to ionizing radiation causes genetic instability, alterations in the cell cycle, apoptosis, or necrosis. Alterations in the G1, S and G2 phases of the cell cycle coincide with improved survival and genome stability. The main cellular factors which are activated by DNA damage and interfere with the cell cycle controls are: p53, delaying the transition through the G1-S boundary; p21WAF1/CIP1, preventing the entrance into S-phase; proliferating cell nuclear antigen (PCNA) and replication protein A (RPA), blocking DNA replication; and the p53 variant protein p53 as together with the retinoblastoma protein (Rb), with less defined functions during the G2 phase of the cell cycle. By comparing a variety of radioresistant cell lines derived from radiosensitive ataxia telangiectasia cells with the parental cells, some essential mechanisms that allow cells to gain radioresistance have been identified. The results so far emphasise the importance of an adequate delay in the transition from G2 to M and the inhibition of DNA replication in the regulation of the cell cycle after exposure to ionizing radiation.

[Analysis of proliferating cell nuclear antigen (PCNA) expression in 24 cases of primary non-small cell pulmonary carcinomas and correlation with survival]

Proliferating cell nuclear antigen (PCNA) is a 36 kD nuclear protein involved in DNA replication that is believed to provide an indication of proliferation in some neoplasms. This study analyzes PCNA expression in 24 cases of primary non-small cell lung cancer using monoclonal PC-10 antibodies in paraffin embedded material. We found significant inter- and intra-tumoral variations in PCNA expression, and no statistically significant relation between the amount of PCNA expression and the size and location of tumors, index of mitosis, histological tumor type or patient age. We found a statistically significant relation (r = 0.47; p < 0.05) between survival and amount of PCNA expression in a sample of 19 cases, but no statistically significant differences in survival related to whether PCNA expression was slight (0-25), moderate (25%-50%) or high (> 50%), and no prognostic value for degree of PCNA expression.

Plasmid insertional mutation may confer glucocorticoid responsiveness of cell growth

Culture of CHO.K1, a Chinese hamster ovary cell line, requires no particular care about the glucocorticoid level in media. Cell growth of CHO.K1 is little affected by dexamethasone at concentrations up to 3 microM. A clone of CHO.K1 stably transfected with an expression vector displayed a favored growth in dexamethasone-containing media. Ironically, dexamethasone was used to trigger the expression of antisense PCNA from the expression vector to impede the cell growth. Proliferating cell nuclear antigen (PCNA), an auxiliary factor of DNA polymerase delta, is required for cell proliferation. The stable cell clone, designated as B11 had a retarded growth rate as compared to its parental cell. However, the B11 cell growth rate and the cell cycle progression were increased by dexamethasone. The glucocorticoid produced no similar effect on the parental cell or other stable transfectants of the same plasmid. Thus, the stimulatory effect of dexamethasone on B11 has little connection with the expression of antisense PCNA and possibly involves a relevant gene in the B11 genome that was mutated due to the random plasmid insertion. A preliminary effort in identifying the targeted gene was made by using plasmid rescue method, and two plasmids were obtained. The rescued DNA of both plasmids specifically hybridized genomic DNA of the parental cells, and one of these plasmids detected a cellular transcript that was absent in B11 cells, suggesting its potential for further investigation.

Significance of proliferating cell nuclear antigen in predicting recurrence of intracranial meningioma

It is well known that the histological appearance of meningiomas often fails to predict accurately the clinical behavior of the tumor. Therefore, attention has turned from tumor histology to tumor biology. Proliferating cell nuclear antigen (PCNA), a cell cycle-regulated protein, has been recently characterized as the cofactor of DNA polymerase-delta, an enzyme required for DNA replication. The rate of synthesis of PCNA directly correlates with the proliferative state of cells. Immunohistochemical labeling of this antigen is now possible with monoclonal antibodies that allow for its demonstration in routinely fixed, paraffin-embedded specimens. In this study, the PCNA labeling index (LI) was determined for 83 meningiomas, including tumors with both benign and malignant clinical courses and with benign, atypical, and malignant histologies, apparent after total or subtotal resections. No statistical difference was found between the LI on recurrence and that found at initial presentation. In addition, stepwise multivariate regression analysis failed to identify any combination of factors (age, gender, race, age of specimen, tumor histology, Simpson grade of resection) that contributes to the predictive strength of the PCNA LI for tumor recurrence. However, for LIs less than 2%, only one of 26 gross totally resected tumors recurred (mean follow up 53 months); for LIs more than 7%, five of 13 gross totally resected tumors recurred (mean follow up 55 months). The difference in recurrence rates between gross totally resected meningiomas with PCNA LIs less than 2% and those with PCNA LIs more than 7% achieved statistical significance with a Fisher's exact probability equaling 0.011. The authors conclude that quantitative PCNA labeling of meningiomas is a promising technique that can provide meaningful prognostic information.

Characterization of a cell cycle-dependent nuclear autoantigen

Analysis of reactivity to nuclear antigens in autoimmune sera revealed a serum that produced a previously undescribed cell cycle-dependent immunofluorescence staining pattern. By indirect immunofluorescence using HEp-2 cells as substrate, the serum generated a speckled and nucleolar pleomorphic staining pattern. This characteristic immunofluorescence pattern was detected in different cell lines from various species indicating that the antigen was highly conserved. This serum immunoprecipitated a 85 kDa protein using an extract from [35S]-labeled HeLa cells. Indirect immunofluorescence of proliferating mouse 3T3 cells displayed the characteristic pleomorphic staining which was not observed in serum-starved cells. Resting human and mouse peripheral blood lymphocytes were negative in immunofluorescence while mitogen-stimulated lymphocytes were positive. Germinal centers of mice two weeks after immunization with 2-phenyl-oxazolone showed speckled immunofluorescence staining in the dark zones whereas unimmunized mice were completely negative. Cell synchronization experiments showed a characteristic sequence of locations of the antigen during the cell cycle. In G1, cells were completely negative. In late G1, G1/S and S phase, speckles were visible. In early G2, speckles were visible, and later in G2, the nucleoli were positive. During mitosis chromosomes were stained. Further characterization of this antibody specificity and cloning of cDNA are in progress.

Expression of proliferating cell nuclear antigen (PCNA) and Ki-67 in soft tissue sarcoma. Is prognostic significance histotype-specific?

Abnormal patterns of proliferation characterize the behavior of many tumors. Proliferating cell nuclear antigen (PCNA) and Ki-67 are two cell cycle antigens which are expressed in proliferative states. Our study examines the prognostic value of these cell-cycle antigens in soft tissue sarcoma (STS). Paraffin-embedded primary tumor tissues from 185 patients (1980-92) were stained with the anti-PCNA antibody PC-10; 182 of these were stained with the antibody MIB-1 for Ki-67. Using PCNA (< or = 50; > 50%) and Ki-67 (< or = 10; > 10%) indices, we examined and compared metastasis-free survival (MFS) in a mixed-histotype group, as well as after subdivision into MFH and non-MFH groups. Fifty-seven patients developed metastases. The median follow-up for survivors was 6 (2-13) years. In the mixed series, the 2-year MFS for a PCNA index < or = 50 was 76%, and for an index > 50 56%. Survival predicted by Ki-67 index was comparable. PCNA index (but not Ki-67) strongly correlated with the incidence of metastasis in MFH tumors and predicted 2-year MFS of 81 vs 48%. In contrast, Ki-67 index (but not PCNA) strongly correlated with metastasis in non-MFH tumors and predicted 2-year MFS survival of 90 vs 45%. No correlation existed between PCNA and Ki-67 indices in the mixed histotype, MFH or non-MFH groups. In combination, a high PCNA and Ki-67 index correlated with poor survival, a high PCNA and lower Ki-67 index (or vice versa) with an intermediate survival, and low PCNA and Ki-67 indices with the best survival. The pattern of PCNA and Ki-67 expression raises the possibility of histotype specificity.

Calcium: a crucial consideration in serum-free keratinocyte culture

This investigation was conducted when previously repeatable experimental data became impossible to reproduce when using keratinocytes cultured in serum-free medium. Differences in calcium molarity between batches of medium were identified as a source of variation in cultured keratinocyte populations. The susceptibility of cultured keratinocytes to even small alterations in calcium molarity has been demonstrated. 2 regular medium batches were compared with a special preparation of medium, devoid of calcium chloride then supplemented with a known concentration of calcium ions. Culture progress in each medium was assessed by: morphological observation, % cells expressing involucrin and proliferating cell nuclear antigen, cell attachment, growth rate and colony forming efficiency. In order to control the phenotype of cultured keratinocytes, in a reproducible system, it is recommended that serum-free keratinocytes medium is purchased with the omission of calcium chloride. Supplementation of this medium may then be made by the investigator to suit individual culture requirements.

Proliferating cell nuclear antigen expression at the invasive tumor margin predicts malignant potential of colorectal carcinomas

BACKGROUND

Proliferative activity may be a useful measure of malignant potential for a variety of tumors. Colorectal carcinomas contain multiple cell populations with different biologic properties. The invasive tumor margin is thought to represent the area with the highest metastatic potential.

METHODS

Cell proliferation at the invasive tumor margin of 49 specimens of advanced colorectal carcinoma was assessed by immunohistochemical staining of proliferating cell nuclear antigen (PCNA) and compared with clinicopathologic findings.

RESULTS

Colorectal carcinomas showed a wide range of PCNA labeling indexes (LI), reflecting variation in proliferative activity. The PCNA LI of tumors showing venous invasion (mean, 51.7% +/- 16.2%) was significantly higher than that of tumors without venous invasion (mean, 36.7% +/- 18.2%; P < 0.01). A strong association was observed between the PCNA LI and the metastatic potential of colorectal carcinoma; the PCNA LI of tumors showing lymph node metastasis (mean, 50.5% +/- 17%) was significantly higher than that of tumors without nodal involvement (mean, 39.8% +/- 18.5%; P < 0.05). In addition, the PCNA LI of tumors metastatic to liver (mean, 55.2% +/- 15.7%) was significantly higher than that of tumors without liver metastasis (mean, 41.0% +/- 17.6%; P < 0.01). Correlation with histologic features at the invasive tumor margin showed that a higher PCNA LI was associated with less differentiated tumors (P < 0.05).

CONCLUSION

Evaluation of the PCNA LI at the invasive tumor margin may help identify colorectal carcinomas that have a higher malignant potential.

Local proliferation of fibroblast-like synoviocytes contributes to synovial hyperplasia. Results of proliferating cell nuclear antigen/cyclin, c-myc, and nucleolar organizer region staining

OBJECTIVE

To test the hypothesis that local proliferation contributes significantly to the hyperplasia of rheumatoid synovium.

METHODS

Immunohistologic and chemical staining was used to identify 3 markers of cell proliferation: proliferating cell nuclear antigen, c-myc proto-oncogene, and nucleolar organizer regions. Synovium from 21 patients with rheumatoid arthritis, 34 with degenerative joint disease, and 7 with joint trauma was examined.

RESULTS

All 3 markers indicated substantial, active proliferation of synovial lining cells in synovium with hyperplasia. Proliferating cells showed type I procollagen immunoreactivity but were negative for CD68, a monocyte/macrophage marker. Proliferation was greater in rheumatoid arthritis than in the other conditions evaluated.

CONCLUSION

In situ proliferation of fibroblast-like synoviocytes in the synovium lining contributes considerably to the increase in cell numbers in rheumatoid synovium.

Cell cycle-associated autoantibodies: markers for autoimmunity and probes for molecular cell biology

Antinuclear autoantibodies are useful diagnostic markers for systemic autoimmune diseases and as probes for the molecular cell biology of nuclear proteins. Here, we review a subset of autoantibodies to nuclear and cytoplasmic proteins involved in the cell cycle. We propose a classification of these autoantibodies into S-phase (DNA Synthesis) and M-phase (Mitosis) autoantibodies. S-phase autoantibodies are represented by autoantibodies to PCNA (Proliferating Cell Nuclear Antigen), the auxiliary protein of DNA polymerase delta. M-phase autoantibodies are represented by autoantibodies to mitotic spindle components viz. centrosomes, condensed chromosomes, centromeres, mitotic spindle proper and intercellular bridge. We have included autoantibodies to nuclear lamins as M-phase autoantibodies as lamins play a key role in reversible breakdown and reformation of nuclear membranes during mitosis. The usefulness of these autoantibodies as diagnostic markers in systemic autoimmune disease is tempered by their presence in patients with "atypical" autoimmune diseases and in normal individuals. However, as molecular probes, they have proven to be unique and invaluable tools for shedding new light on the workings of the cell cycle.